[8f30e3e] | 1 | @c |
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| 2 | @c COPYRIGHT (c) 1988-1998. |
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| 3 | @c On-Line Applications Research Corporation (OAR). |
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| 4 | @c All rights reserved. |
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| 5 | @c |
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| 6 | @c $Id$ |
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| 7 | @c |
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| 8 | |
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| 9 | @chapter Memory Model |
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| 10 | |
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| 11 | @section Introduction |
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| 12 | |
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| 13 | A processor may support any combination of memory |
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| 14 | models ranging from pure physical addressing to complex demand |
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| 15 | paged virtual memory systems. RTEMS supports a flat memory |
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| 16 | model which ranges contiguously over the processor's allowable |
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| 17 | address space. RTEMS does not support segmentation or virtual |
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| 18 | memory of any kind. The appropriate memory model for RTEMS |
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| 19 | provided by the targeted processor and related characteristics |
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| 20 | of that model are described in this chapter. |
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| 21 | |
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| 22 | @section Flat Memory Model |
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| 23 | |
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| 24 | The XXX family supports a flat 32-bit address |
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| 25 | space with addresses ranging from 0x00000000 to 0xFFFFFFFF (4 |
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| 26 | gigabytes). Each address is represented by a 32-bit value and |
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| 27 | is byte addressable. The address may be used to reference a |
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| 28 | single byte, word (2-bytes), or long word (4 bytes). Memory |
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| 29 | accesses within this address space are performed in big endian |
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| 30 | fashion by the processors in this family. |
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| 31 | |
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| 32 | Some of the XXX family members such as the |
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| 33 | XXX, XXX, and XXX support virtual memory and |
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| 34 | segmentation. The XXX requires external hardware support |
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| 35 | such as the XXX Paged Memory Management Unit coprocessor |
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| 36 | which is typically used to perform address translations for |
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| 37 | these systems. RTEMS does not support virtual memory or |
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| 38 | segmentation on any of the XXX family members. |
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| 39 | |
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